Raising Bi-O bands above the Fermi energy level of hole-doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and other cuprate superconductors

TL;DR

This study demonstrates that hole doping in Bi2212 and other cuprates lifts Bi-O bands above the Fermi level, aligning theoretical predictions with experimental observations and revealing a general doping-dependent behavior in cuprate electronic structures.

Contribution

It shows that hole doping lifts Bi-O bands above the Fermi level in Bi2212 and other cuprates, resolving discrepancies between theory and experiment.

Findings

Bi-O bands are lifted above the Fermi level with hole doping.

The theoretical Fermi surface matches experimental data after doping.

Lifting of cation-derived bands is a general property of cuprates.

Abstract

The Fermi surface (FS) of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) predicted by band theory displays Bi-related pockets around the $(\pi,0)$ point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy ($E_F$) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole-doping the Bi-O bands drop below $E_F$ and the system self-dopes below a critical hole concentration. Computations on other Bi- as well as Tl- and Hg-based compounds indicate that lifting of the cation-derived band with hole doping is a general property of the electronic structures of the cuprates.